1. Field of Invention
The present invention relates to a metallic structure and an opto-electronic apparatus. More particularly, the present invention relates to metallic structure and an opto-electronic apparatus for filtering and/or polarizing an electromagnetic wave.
2. Description of Related Art
Filtering of specific frequency spectrum and polarization are basic operations on electromagnetic waves. The materials and devices capable of color filtering and polarization provide important functionality in electro-optical systems, and are often critical parts of electro-optical systems for scientific, engineering, industrial, consumer, defense and many other applications. The peak transmission efficiency and the effective narrowing of the transmission spectrum are important factors for these applications.
The materials used by conventional skills are mostly dielectrics capable of interacting with electromagnetic waves such as dye, organic, plastic, etc., and are often in a form of film. Since decades ago, a net of metal wires were found to be capable of filtering waves within microwave frequency range, and recently has been improved up to far infrared.
Recently, it is found by scientists that the transmittance of electromagnetic waves can be enhanced through subwavelength holes in the metal film. Although the intensity of electromagnetic waves transmitted through the holes can be higher than that impinging on the area of the holes, yet the overall transmitted intensity is only a small fraction (e.g., less than 10%) of the incoming electromagnetic waves partially because the area of the holes is much smaller than the overall area irradiated by the incoming waves.